The state of the art includes the following publications:
US 6621916 B1(SMITH et al.)GB 2059129 A(SODECO)GB 2454821 A(CANADIAN BANK NOTE)EP 1473657 A1(SICPA HOLDING)EP 0981806 A1(CUMMINS-ALLISON)US 5729623 A(OMATU et al.)
The disclosures of all publications and patent documents mentioned in the specification, and of the publications and patent documents cited therein directly or indirectly, are hereby incorporated by reference.